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- Hierarchical fuzzy logic based approach for object trackingPublication . Lopes, Nuno Vieira; Couto, Pedro M.; Jurio, Aranzazu; Melo-Pinto, PedroIn this paper a novel tracking approach based on fuzzy concepts is introduced. A methodology for both single and multiple object tracking is presented. The aim of this methodology is to use these concepts as a tool to, while maintaining the needed accuracy, reduce the complexity usually involved in object tracking problems. Several dynamic fuzzy sets are constructed according to both kinematic and non-kinematic properties that distinguish the object to be tracked. Meanwhile kinematic related fuzzy sets model the object's motion pattern, the non-kinematic fuzzy sets model the object's appearance. The tracking task is performed through the fusion of these fuzzy models by means of an inference engine. This way, object detection and matching steps are performed exclusively using inference rules on fuzzy sets. In the multiple object methodology, each object is associated with a confidence degree and a hierarchical implementation is performed based on that confidence degree.
- Characterization of speed fluctuation and drag force in young swimmers: A gender comparisonPublication . Barbosa, Tiago M.; Costa, Mário J.; Morais, Jorge E.; Morouço, Pedro; Moreira, Marc; Garrido, Nuno D.; Marinho, Daniel A.; Silva, António J.The aim of this study was to compare the speed fluctuation and the drag force in young swimmers between genders. Twenty-three young pubertal swimmers (12 boys and 11 girls) volunteered as subjects. Speed fluctuation was measured using a kinematical mechanical method (i.e., speedo-meter) during a maximal 25-m front crawl bout. Active drag, active drag coefficient and power needed to overcome drag were measured with the velocity perturbation method for another two maximal 25 m front crawl bouts with and without the perturbation device. Passive drag and the passive drag coefficient were estimated using the gliding decay velocity method after a maximal push-off from the wall while being fully immersed. The technique drag index was also assessed as a ratio between active and passive drag. Boys presented meaningfully higher speed fluctuation, active drag, power needed to overcome drag and technique drag index than the girls. There were no significant gender differences for active drag coefficient, passive drag and passive drag oefficient. There were positive and moderate-strong associations between active drag and speed fluctuation when controlling the effects of swim velocity. So, increasing speed fluctuation leads to higher drag force values and those are even higher for boys than for girls.
- Effect of saline environment on mechanical properties of adhesive jointsPublication . Pereira, A. M.; Reis, P.N.B.; Ferreira, J.A.M.; Antunes, F.V.Literature reports very few works about the effect of corrosive environments on the mechanical properties of adhesive joints. Therefore, the present study intends to contribute for a better understanding of the effect of saline solution on the mechanical properties of single-lap adhesive joints. The specimens were manufactured using Docol 1000 high strength steel plates with 1 mm of thickness and Araldite® 420 A/B epoxy adhesive. The static shear strength of the joints was influenced by the exposure time in saline solutions only up to 120 h, and remained, after this period, nearly constant. In terms of fatigue strength, for 105 cycles, a decrease about 25% and 39% occurred in specimens immersed during 120 h in deionised water and saline solution, respectively, comparatively to the control samples.
- Customized crowds and active learning to improve classificationPublication . Costa, Joana; Silva, Catarina; Antunes, Mário; Ribeiro, BernardeteTraditional classification algorithms can be limited in their performance when a specific user is targeted. User preferences, e.g. in recommendation systems, constitute a challenge for learning algorithms. Additionally, in recent years user’s interaction through crowdsourcing has drawn significant interest, although its use in learning settings is still underused. In this work we focus on an active strategy that uses crowd-based non-expert information to appropriately tackle the problem of capturing the drift between user preferences in a recommendation system. The proposed method combines two main ideas: to apply active strategies for adaptation to each user; to implement crowdsourcing to avoid excessive user feedback. A similitude technique is put forward to optimize the choice of the more appropriate similitude-wise crowd, under the guidance of basic user feedback. The proposed active learning framework allows non-experts classification performed by crowds to be used to define the user profile, mitigating the labeling effort normally requested to the user. The framework is designed to be generic and suitable to be applied to different scenarios, whilst customizable for each specific user. A case study on humor classification scenario is used to demonstrate experimentally that the approach can improve baseline active results.
- Hierarchical fuzzy logic based approach for object trackingPublication . Lopes, Nuno Vieira; Couto, Pedro; Jurio, Aranzazu; Melo-Pinto, PedroIn this paper a novel tracking approach based on fuzzy concepts is introduced. A methodology for both single and multiple object tracking is presented. The aim of this methodology is to use these concepts as a tool to, while maintaining the needed accuracy, reduce the complexity usually involved in object tracking problems. Several dynamic fuzzy sets are constructed according to both kinematic and non-kinematic properties that distinguish the object to be tracked. Meanwhile kinematic related fuzzy sets model the object’s motion pattern, the non-kinematic fuzzy sets model the object’s appearance. The tracking task is performed through the fusion of these fuzzy models by means of an inference engine. This way, object detection and matching steps are performed exclusively using inference rules on fuzzy sets. In the multiple object methodology, each object is associated with a confidence degree and a hierarchical implementation is performed based on that confidence degree.
- Computational complexity control for HEVC based on coding tree spatio-temporal correlationPublication . Correa, Guilherme; Assunção, Pedro; Cruz, Luis A. da Silva; Agostini, LucianoThe High Efficiency Video Coding standard shows improved compression efficiency in comparison to previous standards at the cost of higher computational complexity. In this paper, a complexity control method for HEVC encoders based on the dynamic adjustment of the number of constrained coding treeblocks is proposed. The method limits the maximum tree depth used in the coding structures based on spatio-temporal correlation in order to decrease the number of evaluations performed in the Rate-Distortion Optimization process. Experimental results show that the proposed method is capable of maintaining the encoding time per frame under a pre-defined target, reaching computational complexity decreases of up to 50% at the cost of an average BD-PSNR loss of 0.26 dB in the worst case scenario.
- Multiple Description Video Streaming over Asymmetric ChannelsPublication . Correia, Pedro; Assunção, Pedro A. A.; Silva, Vitorhis paper proposes an efficient Unbalanced Multiple Description Scalar Quantisation (U-MDSQ) method for video streaming over asymmetric channels. In order to control the asymmetric target rates for each coded descriptions, the U-MDSQ parameters are combined with the rate control method based on the existing linear relationship between rate and percentage of zeros in transform coefficients in MDSQ domain. The simulation results show that the proposed method exhibits high accuracy for a wide range of target bitrates and unbalanced rates between descriptions. Moreover, the obtained results show the effectiveness of the proposed method in order to improve the overall performance over channels with asymmetric rate and packet loss rate (PLR) conditions, when compared with Balanced MDSQ. This method finds application in video streaming with path diversity based on Multiple Description Coding (MDC) with dynamic channel conditions.
- CrowdTargeting: Making Crowds More PersonalPublication . Costa, Joana; Silva, Catarina; Ribeiro, Bernardete; Antunes, MárioCrowdsourcing is a bubbling research topic that has the potential to be applied in numerous online and social scenarios. It consists on obtaining services or information by soliciting contributions from a large group of people. However, the question of defining the appropriate scope of a crowd to tackle each scenario is still open. In this work we compare two approaches to define the scope of a crowd in a classification problem, casted as a recommendation system. We propose a similarity measure to determine the closeness of a specific user to each crowd contributor and hence to define the appropriate crowd scope. We compare different levels of customization using crowd-based information, allowing non-experts classification by crowds to be tuned to substitute the user profile definition. Results on a real recommendation data set show the potential of making crowds more personal, i.e. of tuning the crowd to the crowdtarget.
- Constrained encoding structures for computational complexity scalability in HEVCPublication . Correa, Guilherme; Assunção, Pedro; Cruz, Luis A. da Silva; Agostini, LucianoThe High Efficiency Video Coding standard shows improved compression efficiency in comparison to previous standards at the cost of higher computational complexity. In this paper, a complexity scalability method for HEVC encoders based on the dynamic adjustment of the number of constrained coding treeblocks is proposed. The method limits the Prediction Unit shapes and the maximum tree depth used in each Coding Treeblock in order to decrease the number of evaluations performed in the Rate-Distortion Optimization process. The encoder is capable of trading off computational complexity and compression efficiency while still maintaining the encoding time per Group of Pictures (GOP) under a pre-defined target. The encoding complexity can be decreased in up to 60% when compared to the original encoder at the cost of small Bjontegaard Delta (BD)-rate increases.
- The influence of cadmium contamination and salinity on the survival, growth and phytoremediation capacity of the saltmarsh plant Salicornia ramosissimaPublication . Pedro, Carmen; Santos, Márcia S.S.; Ferreira, Susana; Gonçalves, Sílvia C.The major aim of this study was to evaluate the capacity of Salicornia ramosissima on Cadmium phytoremediation under distinct salinities and, consequently, the toxic effects on the plant’s development. A greenhouse experiment was performed, using two Cd concentrations (50 and 100 mg l 1) in different salinities (0, 5 and 10). Mortality and weight variation, observed at the end of the experiment, showed significant differences between some treatments, meaning that these variables were affected by the salinity and Cd concentrations. The highest Cd accumulation was detected in the roots, and decreased with the increase of salinity and Cd concentration. S. ramosissima is a potential candidate for Cd phytoremediation at salinities close to 0 and its capabilities in Cd phytoaccumulation and phytoestabilization proved to be quite interesting. The optimization of phytoremediation processes by S. ramosissima could turn possible the use of this plant in the recovery of contaminated ecosystems.